Production printing systems for high-volume printing typically utilize a production printer that marks a continuous-forms print medium (e.g., paper) with a wet colorant (e.g., an aqueous ink). After marking the continuous-forms print medium, a dryer downstream from the production printer is used to dry the colorant applied to the continuous-forms print medium. Microwave dryers may be employed as a dryer for a production printing system in some applications.
A microwave dryer utilizes microwave energy to heat the colorant to cause a liquid portion of the colorant to evaporate, thereby fixing the colorant to the continuous-forms print medium. A microwave source directs the microwave energy down a long axis of a waveguide, and a passageway through the waveguide is sized to enable the continuous-forms print medium to pass through the waveguide. As the continuous-forms print medium traverses the passageway, wet colorant applied to the continuous-forms print medium is exposed to the microwave energy and is heated.
To achieve a sufficient level of drying, microwave dryers generate a substantial amount of microwave radiation. This microwave radiation must be blocked before it exits the microwave dryer in order to ensure that the microwave radiation is contained within the desired dryer operating areas and that components external to the dryer are not heated by microwaves. At the same time, it remains important to reduce the path length occupied by drying systems in order to save space within a print shop.